The invention relates to a method of manufacturing a molded product of multiple-component mainly composed of waste plastics or wastepaper, and presents a method of recycling materials without having to classify waste plastics. For example, by processing into a material board, a panel usable as substitute for building material or civil engineering material is presented.
Industrial waste and domestic waste were once products made of various materials such as plastics, and for recycling of resources, it is required to separate and classify the materials, and single materials being separated and classified are collected as recycled resources. In particular, plastic materials have problems of specificity as high molecular binders, and it has been considered impossible to mix different materials, and fuse and mold again according to the theory of compatibility, and if fused and molded, the required strength as product could not be obtained sufficiently.
For example, in the case of recycling of PET bottles, the main body resin is integrally molded of polyethylene terephthalate resin (PET resin), but the label area is made of polystyrene resin (PS) in consideration of printability. The cap is made of polypropylene resin (PP) in consideration of moldability, and the PET bottles made of three materials are separated and classified, and the PET resin of the main body is processed into fibers, and used in weaving of carpets, working clothes, etc. at the present.
Waste plastics from automotive parts are treated for oiliness, and recycled as the liner of automobile carpets or undercoating agent for the bottom of the car body in the factories of, the major automakers at the present, but it is not intended to recycle waste plastics discharged in the general market, and examples of recycling into building materials in a different market are not known yet.
Moreover, building plywoods were mainly wood bonds using tropical woods, and products were mainly composed of wood materials and wood pieces such as veneer, plywood, particle board, fiberboard, wood piece cement board, and gypsum particle board, and conifer woods are pressed and adhered by using adhesive as in particle board and fiberboard at the present. For example, as disclosed in Japanese Laid-open Patent No. 8-93217, resin plywoods made of rigid urethane resin are also developed, but they are also integrally molded by extrusion by laminate fusing method of injection molding method by adhering resin sheets, and the resin materials used therein are only single resins which are used by fusing and molding.
Although effective utilization of resources is requested, the recycling rate of waste plastics is only 2.9%, or 260,000 tons a year (1996). The rest is processed by methods causing to produce carbon dioxide such as use as fuel or incineration. The recycling rate of wastepaper is 53.5% (15 million tons), and this rate is not improved for several years.
The problem is that recycling requires separation and classification of waste matter composed of various materials, and the present processing method is limited for recycling as single materials. Concerning waste plastics, 300 to 1000 kinds of plastic resins are distributed in market, and once released into the market, it is nearly impossible to identify the materials in most resins.
Plastics are also called high molecular binders, and high polymers of different kinds are not miscible in the molecular order like water and oil. For example, polystyrene and polypropylene are similar in structural formula, but are not compatible. Thus being composed of multiple different molecular bonds, it is impossible to disperse different materials in the monomer units, and fuse mutually and mold again according to the theory of compatibility. If fused and molded, it is extremely difficult to satisfy the physical strength required in the product.
It is hence an object of the invention to present a method of manufacturing molded products by using waste plastics, wastepaper, wood pieces and others commonly, without sorting out from the refuse, by solving the problems mentioned above, and to present molded products of light weight for volume and having a sufficient strength at low cost by such method.
Plastic materials composed of noncompatible different polymers are formed into cellulose in sledge form to obtain cotton-like polymers, and mutually woven cellulose fibers are fused under heat and pressure, so that noncompatible different polymers can be integrally kneaded and molded. Herein, this molding method is called the cellulose molding method.
As different fibers in sledge form are woven together, high molecular meshes of different kinds are formed, and noncompatible different resins are used and molded again, and if aggregation begins due to temperature changes, since plastic fibers in compatible relation are woven together, peeling phenomenon can be avoided.
Further, by opening wastepaper, wood pieces and others, fibers having molecular skeleton containing cellulose, hemicellulose, lignin and others can be obtained.
Such fine fibers and plastic fibers are mutually woven and fused, and lignin is eluted to permeate into gaps of microphase separation of plastic fibers, so that an integral molded product is composed. Further, the cellulose failing to elute is mixed into the molded product as cellulose fibers, so that the physical strength may be satisfied.
Considering recycling of waste plastics, hitherto, it was general to grind plastics into fine pieces and fuse. High molecules of different kinds are not mutually fused in he molecular order like water and oil. For example, polystyrene and polypropylene are similar in structural formula, but are not compatible. Such fusible relation of plastics is generally understood as compatible relation or noncompatible relation. If fused, however, it is extremely difficult to satisfy the strength and other physical properties required in the product. FIG. 4A and/or FIG. 4B shows a sample of fusing and molding different resins. In this case, using a biaxial extruder, polystyrene (outside) and polypropylene (inside) are extruded and spun, and the fusing temperature was 220 deg. C. in polystyrene and 180 deg. C. in polypropylene. The discharge was 2.4 cc/cycle, and interface tension was 5.1 mN/m. In the diagram, the polystyrene phase and polypropylene phase form an independent layer individually without being fused together. independent layer individually without being fused together.
On the other hand, known as polymer alloy, plastic materials are widely modified as new materials by mixing various components. Many practical examples are known. For example, the ABS resin widely used in automotive parts is known as a representative polymer alloy by copolymerization of polystyrene with butadiene or styrene. However, the forming method of polymer alloy is generally a chemical bond processing in a chemical plant, such as graft copolymerization or block copolymerization, and it is possible only by specifying the raw materials in both quality and quantity, and further using a solvent, and therefore in the case of waste plastics, if the quality and quantity of raw materials cannot be specified, it is difficult to obtain a product (molded product) satisfying the required quality, strength and other properties.
As other method, when different materials are fused and kneaded mechanically and by force, using an extruder or the like, a two-phase sea-island structure in emulsion form (see FIG. 5a, FIG. 5b, FIG. 5C and/or FIG. 5d.) is obtained, and it can be cooled and solidified, but since the surface tension between high molecules is small, as the noncompatible plastic resin aggregates by temperature change, phase separation begins, and peeling phenomenon may occur (note also page 10).
By such method, a fused product may be obtained by mixing different materials, but since the quality, quantity and properties of waste plastics cannot be determined, and hence the solvent cannot be specified, so that a perfect polymer alloy cannot be formed, and it was difficult to recycle the refuse.
According to the cellulose forming method of the invention, by forming plastic materials composed of noncompatible different polymers into cellulose in thread form, linear polymers are obtained, and by kneading fibers made of different materials, different types of high molecular meshes are formed, and the mutually woven cellulose fibers are fused under heat and pressure, so that noncompatible different polymers are integrally kneaded to form into a desired shape (see FIG. 3). By mutually weaving different fibers in thread form, different types of high molecular meshes are formed, and microphase separation phenomenon recurs, but by maintaining the physical composition and forming multi-phase material constitution, it was found that the rigidity superior to that of single material can be obtained.
Moreover, by physically opening wastepaper, wood pieces and others, fibers having molecular skeleton containing cellulose, hemicellulose, lignin and others can be obtained. When such fine fibers and plastic fibers are mutually woven and fused, and lignin is eluted to permeate into gaps of microphase separation of plastic fibers, so that an integral molded product is composed. Further, the cellulose failing to elute is mixed into the molded product as cellulose fibers, so that the physical strength may be satisfied.
When plastic fibers formed by fusing and spinning plastics in sledge form and fibers obtained by opening wastepaper, wood pieces and others are fused under heat and pressure, a crosslinking effect is brought about in the microphase separation situation of waste plastics in noncompatible relation, so that a material board having properties similar to those of wood can be obtained from the refuse.
Since the molded product of the invention is mainly composed of waste matter such as waste plastics and wastepaper, it is low in cost and excellent in processability. In particular, by mixing wastepaper, aside from waste plastics, the molded product is light in weight for its volume. Having the characteristics of thermoplastic resin, peeling performance from concrete is excellent, and the water resisting effect is sufficient. Moreover, as required, coloring pigment, antistatic agent, foaming agent (for reducing weight), magnetic powder (for shielding effect of electromagnetic waves), and others may be fused together, so that it can be used as substitute for building plywood or the like.
According to the invention, as refuse processing and recycling method, using waste plastics and wastepaper as principal materials, a molding method of low cost, specific strength and excellent processability may be presented, and by effectively utilizing waste plastics and waste paper, it also contributes to the industrial waste problem and environmental problem.
Further, by using the molded product of the invention as a substitute for plywood for building or civil engineering, since wood is not used in the material as in the conventional plywood, the present problem of forest protection may be partly solved. It is preferable, for example, as the substitute for plywood for concrete forms. By employing the cellulose forming technology of the invention, wastepaper can be mixed and fused into waste plastics, and a material board similar to plywood can be recycled from the refuse.